Background print agent enclosed region removal

Abstract

In one example in accordance with the present disclosure, a printing device is described. The printing device includes a print controller with a processor and memory. The print controller generates print instructions. Specifically, the print controller receives print image data representing an image to be printed and identifies enclosed regions in a background print agent plane. The print controller also determines a size of the enclosed regions of background print agent plane and responsive to the size of an enclosed region being smaller than a threshold size, removes the enclosed region from the background print agent plane. The printing device also includes a print agent distribution system to apply the background print agent and the image print agent to a substrate according to the print instructions.

What is claimed is: 
     
       1. A printing device, comprising:
 a print controller comprising a processor and memory, the print controller to generate print instructions by:
 receiving print image data representing an image to be printed; 
 identifying, in the print image data, enclosed regions in a background print agent in a background print agent plane; 
 determine a size of the enclosed regions of background print agent; and 
 responsive to the size of an enclosed region being smaller than a threshold size, removing the enclosed region from the background print agent plane; and 
 
 a print agent distribution system to apply the background print agent and the image print agent to a substrate according to the print instructions. 
 
     
     
       2. The printing device of  claim 1 , wherein the print controller is to restore removed enclosed regions where a size of a connected component formed of dilated enclosed regions is greater than a threshold size. 
     
     
       3. The printing device of  claim 1 , wherein the print controller is to:
 identify, a coincident edge region between the background print agent plane and an image print agent plane, wherein the coincident edge region is an edge in an area to be printed with both the background print agent and the image print agent; and 
 selectively modify at least one of the background print agent plane and the image print agent plane in a vicinity of the identified coincident edge region to determine a modified plane. 
 
     
     
       4. The printing device of  claim 3 , wherein selectively modifying at least one of the background print agent plane and the image print agent plane in a vicinity of the identified coincident edge region to determine a modified plane comprises:
 performing a pixel erosion operation along the identified coincident edge region in the background print agent plane; and 
 determining whether there is a local region of background print agent that will be less than a threshold size following the erosion and, when at least one such region is identified, excluding the identified local region from the pixel erosion operation. 
 
     
     
       5. The printing device of  claim 1 , wherein the print controller is to identify a subset of locations as candidate locations for enclosed regions. 
     
     
       6. The printing device of  claim 1 , wherein the print controller is to identify areas of the print image from the print image data for which the removal of enclosed regions is to be undone. 
     
     
       7. A method, comprising:
 receiving, at a printing device, print image data representing an image to be printed; 
 identifying, from the print image data, enclosed regions in a background print agent in a background print agent plane; 
 determine a size of enclosed regions of the background print agent; 
 responsive to the size of an enclosed region being smaller than a threshold size, removing the enclosed region from the background print agent plane; and 
 applying the background print agent and the image print agent to a substrate according to the print instructions. 
 
     
     
       8. The method of  claim 7 , further comprising:
 identifying areas of the print image wherein a removal of the enclosed regions is to be undone; and 
 undoing the removal of enclosed regions within identified areas. 
 
     
     
       9. The method of  claim 8 , wherein identifying regions of the image where the enclosed regions are to be restored comprises:
 expanding and eroding the enclosed regions by a threshold amount; 
 identifying those enclosed regions that overlap to form a connected component; and 
 responsive to a connected component area being greater than a threshold area, identifying the connected component as a region of the image to be restored to the background print agent plane. 
 
     
     
       10. The method of  claim 7 , further comprising altering the threshold size based on user input. 
     
     
       11. The method of  claim 7 , further comprising:
 identifying a coincident edge region in the background print agent plane and an image print agent plane, wherein the coincident edge region is an edge in an area to be printed with both the background print agent and the image print agent; 
 performing a pixel erosion operation along the identified coincident edge region in the background print agent plane; and 
 determining whether there is a local region of background print agent that will be less than a threshold size following the erosion and, if at least one such region is identified, excluding the identified local region from the pixel erosion operation. 
 
     
     
       12. A non-transitory machine-readable storage medium encoded with instructions executable by a processor, the machine-readable storage medium comprising instructions to:
 receive print image data representing an image to be printed; 
 generate a binary threshold image wherein regions that are to receive a background print agent is in a first color and regions that are not to receive a background print agent is in a second color; 
 determine from the binary threshold image:
 enclosed regions in a background print agent plane; and 
 a size of each enclosed region of background print agent plane; 
 
 responsive to a size of an enclosed region being less than a threshold size removing the enclosed region from the background print agent plane; and 
 apply the background print agent and the image print agent to a substrate according to the print instructions. 
 
     
     
       13. The non-transitory machine-readable storage medium of  claim 12 , further comprising instructions, executable by the processor, to store indices of the enclosed regions. 
     
     
       14. The non-transitory machine-readable storage medium of  claim 13 , further comprising instructions, executable by the processor to:
 expand and erode the enclosed regions by a threshold amount; 
 identify those enclosed regions that overlap to form a connected component; and 
 responsive to a connected component area being greater than a threshold area, identifying the connected component as a region of the image to be restored to the background print agent plane. 
 
     
     
       15. The non-transitory machine-readable storage medium of  claim 13 , wherein removal of enclosed regions of the background print agent plane is performed on areas of the background print agent plane that have been eroded to fall underneath the image print agent plane.